Bring a large stockpot of salted water to a boil and cook pasta shells al dente, according to the package directions (usually 12 minutes.)

Meanwhile, put frozen spinach in a microwave-safe dish with a lid. Cover and microwave on high about 5 minutes. Remove lid and set aside to cool.

In a non-stick skillet with a lid, heat olive oil on medium. Saute onion for 2 minutes, until brown on edges. Reduce heat to low. Stir in garlic and mushrooms. Cover and let simmer for 10 minutes.

Place tofu in a medium-size mixing bowl. Sprinkle lemon juice over tofu and stir with a fork, crumbling tofu into small curds that resemble ricotta cheese. While tofu marinates in juice, drain the spinach. Squeeze all the excess water out of the spinach, one handful at a time.

Preheat oven to 375. Spread spaghetti sauce in the bottom of a 12x8" baking dish. Gently spoon vegetable-tofu filling into the shells. Arrange in tight rows on top of the sauce. Bake for 15 minutes on the middle rack. Raise oven heat to broil. Sprinkle shells with pine nuts and broil (still on middle rack) for 5 minutes.

Serve warm with garlic bread and a green salad.

Helpful Tips:

Note: I wanted my family to enjoy the health benefits of soy protein and tofu. So, I converted a traditional stuffed shells recipe, substituting tofu for ricotta cheese. The tofu breaks into tiny curds that anyone will assume is ricotta cheese. And the dish is so full of flavor that no one will question the secret ingredient! The end result is a healthier, low-fat, great tasting recipe that will please any tofu-phobe!